What is LAPB (Link Access Procedure?
Link Access Procedure, Balanced ( LAPB) implements the data link layer as defined in the X.25 protocol suite. LAPB is a bit-oriented protocol derived from HDLC that ensures that frames are error free and in the correct sequence.
What is LAPB used for?
Link Access Protocol, Balanced (LAPB) is used to manage communication and packet framing between data terminal equipment (DTE) and the data circuit-terminating equipment (DCE) devices in the X.25 protocol stack. LAPB is nothing but HDLC in Asynchronous Balanced Mode (ABM).
What is the full form of LAPB?
Description Link Access Procedure, Balanced (LAPB) Complete Definition LAPB is a bit-oriented protocol derived from HDLC that ensures that frames are error free and in the right sequence. Link Access Protocol, Balanced (LAPB) is used to manage
What are the modes of operation of LAPB?
Modes of operation – LAPB works in the Asynchronous Balanced Mode (ABM). This mode is balanced (i.e., no master/slave relationship) and is signified by the SABM (E)/SM frame. Each station may initialize, supervise, recover from errors, and send frames at any time. The DTE and DCE are treated as equals.
What is the binary pattern for a LapB?
The binary pattern 01111110 is used to mark the beginning of the LAPB frame. This pattern has to be be unique so the transmitter in a LAPB connection uses a bit stuffing technique to make sure that the flag pattern appears only in the flag fields.
What is a LAPB frame?
LAPB frames contian a header, encapsulated data, and a trailer. The diagram below shows the format of the of the LAPB frame and its relationship to the Protocol Layer Packet (PLP) and the X.21bis frame. The following descriptions summarize these fields:
What is link access procedure?
Link Access Procedure, Balanced (LAPB) is a reliable synchronous serial protocol used to manage packet framing between DTE and DCE stations. LAPB supports several protocols including X.25, Frame Relay and ATM. LAPB is capable of placing frames in the correct order, as well as checking packets for errors (error detection) and thus releives higher level protocols from having to perform these functions.
What is the PLP protocol?
The network layer protocol called the Packet Layer Protocol (PLP), which defines how to address and deliver X.25 packets between end nodes and switches on an X.25 network using permanent virtual circuits (PVCs) or switched virtual circuits (SVCs). This layer is responsible for call setup and termination and for managing transfer of packets.
What is link access protocol?
The data-link layer protocol called Link Access Procedure, Balanced (LAPB), which defines encapsulation (framing) and error-correction methods. LAPB also enables the DTE or the DCE to initiate or terminate a communication session or initiate data transfer. LAPB is derived from the High-level Data Link Control (HDLC) protocol.
